Graphene MoS2 Hybrid Research Articles

Fano resonance in graphene-MoS2 heterostructure-based surface plasmon resonance biosensor and its potential applications

We propose a new configuration of surface plasmon resonance (SPR) sensor that is based on graphene-MoS2 hybrid structures for ultrasensitive detection of molecules. The present configuration is consisted of chalcogenide glass (2S2G) prism, Ag, coupling layer, guiding layer, graphene-MoS2 heterostructure and analyte. We perform numerical and analytical study of the impact of the thickness and refractive index (RI) of the coupling and guiding layer in a planar sensing structure within the Kretschmann configuration on the resonance properties of the excitation. Results of reflectivity calculations clearly demonstrate the sharp Fano-type resonance appears in the curve of SPR because of the coupling between surface plasmon polariton (SPP) and planar waveguide (PWG) modes. The properties of the Fano resonance (FR) strongly depend on the parameters of the structure. The calculated magnetic field profiles manifest that the hybrid nature of the electromagnetic (EM) modes excited in the present structure. The proposed system displays an enhancement factor of sensitivity by intensity more than 2 × 103-fold when compared to the SPR sensing scheme.

Sensitivity Enhanced by MoS2–Graphene Hybrid Structure in Guided-Wave Surface Plasmon Resonance Biosensor

Compared with surface plasmon resonance (SPR) biosensor, guided-wave surface plasmon resonance (GWSPR) biosensor has a higher sensitivity. In order to further enhance the sensitivity of the GWSPR biosensor, the MoS2–graphene hybrid structure is proposed to cover on the surface of the thin silicon film. It is demonstrated that the sensitivity of the proposed biosensor configuration can be doubled by using optimized MoS2–graphene hybrid structure. By analyzing the electric field distributions with the proposed GWSPR biosensor, it is shown that the electric field intensity has a dramatic change with a slight change in refractive index of sensing medium, and it also means that the biosensor is sensitive to detect the analytes. Moreover, the proposed GWSPR biosensor has a wide detection range of refractive index of sensing medium, and the sensitivity is increased with the refractive index of sensing medium increasing.

3D MoS2-graphene hybrid aerogels as catalyst for enhanced efficient hydrogen evolution

Aerogel composite materials consisting of MoS2 and reduced graphite oxide (rGO) are synthesized by a facile general hydrothermal method, where GO is utilized as a template and provides a novel substrate for the nucleation and subsequent growth of MoS2. These MoS2/rGO hybrid nanostructures exhibit three-dimensional (3D) leaf-like morphology, and show excellent electrocatalytic activities of hydrogen evolution reaction (HER), with a low overpotential of approximately 105mV, a small Tafel slope of 51mV/dec and a large exchange current density (j0) of 3.28×10−5A/cm2. The superior electrochemical performance should be attributed to the 3D porous MoS2/rGO hybrid architecture, which enhances the conductivity from graphene to MoS2 as well as the HER activity.

Rational design of multifunctional devices based on molybdenum disulfide and graphene hybrid nanostructures

We rationally designed a new type of hybrid materials, molybdenum disulfide (MoS2) synthesized by Mo pre-deposition followed by subsequent sulfurization process directly on thermal chemical vapor deposition (TCVD)-grown graphene, for applications in a multifunctional device. The synthesis of stoichiometric and uniform multilayer MoS2 and high-crystalline monolayer graphene was evaluated by X-ray photoelectron spectroscopy and Raman spectroscopy. To examine the electrical transport and photoelectrical properties of MoS2-graphene hybrid films, field effect transistors (FETs) and visible-light photodetectors based on MoS2-graphene were both fabricated. As a result, the extracted mobility for MoS2-graphene hybrid FETs was two times higher than that of MoS2 FETs. In addition, the MoS2-graphene photodetectors revealed a significant photocurrent with abrupt switching behavior under periodic illumination.

Graphene-MoS2 Hybrid Structure Enhanced Fiber Optic Surface Plasmon Resonance Sensor

In this paper, a fiber optic surface plasmon resonance sensor based on graphene-MoS2 hybrid structure is presented. The wavelength interrogation method is employed to analyze the reflection spectra and the performance of the sensor. The theoretical analysis shows that the confined electric field generated at the interface between the sensor surface and the surrounding environment can be enhanced by introducing graphene-molybdenum disulfide (MoS2) hybrid structure as the sensing layers coated on the core of fiber. Such electric field enhancement significantly improves the sensitivity of the fiber optic surface plasmon resonance sensor. Furthermore, it is suggested that coating more number of graphene and MoS2 layers on thicker Au film is a good selection for the higher enhancement of the sensitivity. The sensitivity of the proposed sensor exhibits an enhancement of 20 % compared to that of the conventional fiber optic surface plasmon resonance sensing scheme without graphene-MoS2 hybrid structure. The proposed graphene-MoS2-Au fiber optic surface plasmon resonance sensor is simple in structure, has high sensitivity, and shows good potential in practical applications.

Hybrid graphene–molybdenum disulphide based ring resonator for label-free sensing

In this paper, a novel graphene–MoS2 hybrid structure based surface plasmon resonance sensor is presented for label-free analysis. The structure consists of a silicon nitride (Si3N4) dielectric layer vertically coupled to a thin layer of metallic strip made of silver (Ag) on top. A hybrid graphene–MoS2 layer is added on top of the metallic strip to enhance the sensitivity and the quality factor of the sensor. The cladding layer is assumed to be porous alumina (p-Al2O3) increasing the interaction of the surface plasmon mode and the target molecules. Finite difference time domain analysis (FDTD) has been used to design and to analyze the performance of the sensor. It is shown that by addition of hybrid graphene–MoS2 layer to the structure of a surface plasmon resonance based sensor, the refractive index sensitivity and the intrinsic quality factor of the sensor are enhanced simultaneously. It is also shown that addition of the hybrid graphene–MoS2 layer leads to higher values of figure of merit (FOM) for the sensor, and consequently better performance of the sensor. Moreover, the effect of increasing the number of graphene and MoS2 layers is investigated. The proposed sensor is very compact and can be used for lab-on-a-chip sensing applications.

Monolayer MoS2-Graphene Hybrid Aerogels with Controllable Porosity for Lithium-Ion Batteries with High Reversible Capacity.

Monolayer MoS2 nanosheets (NSs) are promising anode materials for lithium-ion batteries because all redox reactions take place at the surface without lithium-ion diffusion limit. However, the expanded band gap of monolayer MoS2 NSs (∼1.8 eV) compared to their bulk counterparts (∼1.2 eV) and restacking tendency due to the van der Waals forces result in poor electron transfer and loss of the structure advantage. Here, a facile approach is developed to fabricate the MoS2-graphene aerogels comprising controlled three-dimensional (3D) porous architectures constructed by interconnected monolayer MoS2-graphene hybrid NSs. The robust 3D architectures combining with the monolayer feature of the hybrid NSs not only prevent the MoS2 and graphene NSs from restacking, but also enable fast electrode kinetics due to the surface reaction mechanism and highly conductive graphene matrix. As a consequence, the 3D porous monolayer MoS2-graphene composite aerogels exhibit a large reversible capacity up to 1200 mAh g(-1) as well as outstanding cycling stability and rate performance, making them promising as advanced anode materials for lithium-ion batteries.

MoS2-graphene hybrid nanosheets constructed 3D architectures with improved electrochemical performance for lithium-ion batteries and hydrogen evolution

ABSTRACT Advanced materials for energy conversion and storage are central to clean and reliable energy research. Herein, three-dimensional (3D) architectures composed of MoS 2 -graphene hybrid nanosheets are synthesized via a simple solvothermal method for this purpose. The architectures are self-assembled with hybrid nanosheets, which are fabricated through the in situ growth of few-layer MoS 2 nanosheets on the surface of graphene substrates. Rooted in the intriguing advantages of sheet-on-sheet structures and 3D features, the composite materials exhibit improved electrochemical lithium storage performances when used as anode materials, in terms of high reversible capacity, superior cycling stability (904 mAh g −1 after 200 cycles at 200 mA g −1 ), and high rate capability. It is also employed as integrated electrode for electrochemical water splitting and delivers remarkably enhanced catalytic performance for hydrogen evolution, such as low onset overpotential (110 mV), small Tafel slope (47 mV decade −1 ), and stable cycling performance.

Sensitivity enhancement of surface plasmon resonance sensor based on graphene–MoS2 hybrid structure with TiO2–SiO2 composite layer

In this paper, surface plasmon resonance (SPR) sensor based on graphene–MoS2 hybrid structure with composite layer of TiO2–SiO2 is presented. The angular interrogation method is used for the analysis of reflected light from the sensor. For the calculation of the sensitivity, first of all the thicknesses of TiO2, SiO2 and gold layers are optimized for the monolayer graphene and MoS2. Thereafter, at these optimum thicknesses the reflectance curves are plotted for different sensor structure and comparison of change in resonance angle is made among these structures. It is observed that the sensitivity of the graphene–MoS2-based sensor is enhanced by 9.24 % with respect conventional SPR sensor. The sensitivity is further enhanced by including TiO2–SiO2 composite layer between prism base and metal layer and observed that the enhanced sensitivity for this sensor is 12.82 % with respect to conventional SPR sensor and 3.28 % with respect to graphene–MoS2-based SPR sensor. At the end of this paper, the variation of the sensitivity and minimum reflectance is plotted with respect to sensing layer refractive index at the optimum thickness of all the layers and optimum number of MoS2 and graphene layers. It is also observed that four layers of MoS2 and monolayer graphene are best selection for the maximum enhancement of the sensitivity.

Performance of graphene–MoS2 based surface plasmon resonance sensor using Silicon layer

In this paper a graphene–MoS2 hybrid structure based surface plasmon resonance biosensor is presented. The performance parameters of the proposed sensor are defined in terms of sensitivity, detection accuracy and quality factor. By the addition of hybrid graphene–MoS2 layer the sensitivity is enhanced but the quality factor and detection accuracy is decreased. Hence to increase the quality factor and detection accuracy a silicon layer is included between metal and MoS2 layer. It is observed that the full width at half maximum of reflectance curve is minimized up to great extent with little decrement in the sensitivity due to the inclusion of silicon layer. Furthermore in this paper, the effect of increasing the number of layers of graphene and MoS2 is also analyzed.

A self-powered graphene–MoS2 hybrid phototransistor with fast response rate and high on–off ratio

Here, we present a self-powered graphene–MoS2 hybrid phototransistor that simultaneously exhibits high responsivity, fast response rate and high on–off ratio. In this phototransistor, fewer-layer MoS2 serves as a sensitizer to absorb light, and high mobility graphene serves as an expressway for carrier transport, an asymmetric metal contact (titanium and palladium) design is adopted to provide a strong internal electric-field in the phototransistor channel. Under light illumination, a photovoltage arises at the two asymmetric graphene/electrode interface with photodiode mechanism, which act as a bias voltage driving the large quantity of photocarriers injected from MoS2 layer to transport in graphene channel with photoconductor mechanism. With this ingenious design, the hybrid phototransistor achieves a response rate of 0.13ms and on–off ratio up to 1428 together with responsivity exceeding 3.0A/W under zero bias operation. The hybrid phototransistor takes full the advantage of fast response rate of the photodiode and high responsivity of the photoconductor, which makes it has great potential for wide applications in optoelectronics, such as optical logic, optical computing and optical communication.

The stability and electronic properties of novel three-dimensional graphene-MoS2 hybrid structure.

Three-dimensional (3D) hybrid layered materials receive a lot of attention because of their outstanding intrinsic properties and wide applications. In this work, the stability and electronic structure of three-dimensional graphene-MoS2 (3DGM) hybrid structures are examined based on first-principle calculations. The results reveal that the 3DGMs can easily self-assembled by graphene nanosheet and zigzag MoS2 nanoribbons, and they are thermodynamically stable at room temperature. Interestingly, the electronic structures of 3DGM are greatly related to the configuration of joint zone. The 3DGM with odd-layer thickness MoS2 nanoribbon is semiconductor with a small band gap of 0.01–0.25 eV, while the one with even-layer thickness MoS2 nanoribbon exhibits metallic feature. More importantly, the 3DGM with zigzag MoS2 nanoribbon not only own the large surface area and effectively avoid the aggregation between the different nanoribbons, but also can remarkably enhance Li adsorption interaction, thus the 3DGM have the great potential as high performance lithium ion battery cathodes.

Graphene–MoS2 hybrid nanostructures enhanced surface plasmon resonance biosensors

In this work, we propose a new configuration of surface plasmon resonance (SPR) sensor that is based on graphene–MoS2 hybrid structures for ultrasensitive detection of molecules. The proposed system displays a phase-sensitivity enhancement factor of more than 500-fold when compared to the SPR sensing scheme without the graphene–MoS2 coating or with only graphene coating. Our hypothesis is that the monolayer MoS2 has a much higher optical absorption efficiency (∼5%) than that of the graphene layer (∼2.3%). Based on our findings, the electron energy loss of MoS2 layer is comparable to that of graphene and this will allow a successful (∼100%) of light energy transfer to the graphene–MoS2 coated sensing substrate. Such process will lead to a significant enhancement of SPR signals. Our simulation shows that a quasi-dark point of the reflected light can be achieved under this condition and this has resulted in a steep phase jump at the resonance angle of our newly proposed SPR system. More importantly, we found that phase interrogation detection approach of the graphene–MoS2 hybrid structures-based sensing system is more sensitive than that of using the regularly angular interrogation method and our theoretical analysis indicates that 45nm of Au film thickness and 3 coating layers of MoS2 nanosheet are the optimized parameters needed for the proposed SPR system to achieve the highest detection sensitivity range.

Fabrication of three-dimensional MoS2-graphene hybrid monoliths and their catalytic performance for hydrodesulfurization

A simple process to synthesize three-dimensional molybdenum disulfide-graphene monolithic catalysts (3D-MoS2-G) was developed. 3D-MoS2-G hybrid monoliths were fabricated by a combined hydrothermal self-assembly and freeze-drying treatment, in which ammonium tetrathiomolybdate and graphite oxide were used as starting materials. The structure and morphology of the samples were characterized by X-ray diffraction, Fourier transform infrared spectrometry, Raman spectrometry, field emission scanning electron microscopy, transmission electron microscopy and nitrogen adsorption. The catalytic performance of the hybrid monoliths was investigated by evaluating the activity for the hydrodesulfurization (HDS) of carbonyl sulfide (COS). In addition, the influence of microwave irradiation on the catalytic property of the 3D-MoS2-G monoliths was also investigated. It is demonstrated that after microwave irradiation the 3D-MoS2-G monoliths show an excellent activity for COS hydrogenation compared with the traditional MoS2/γ-Al2O3 catalyst prepared by impregnation-sulfidation. The 3D-MoS2-G-160 M monolith hydrothermally synthesized at 160 °C exhibits the highest COS conversion of 100% at a relatively low temperature (260 °C) for the HDS reaction. The superior performance of the 3D-MoS2-G-160 M catalyst can be ascribed to the unique hybridized structure of the MoS2 nanoparticles uniformly dispersed on graphene sheets in the monolith. [New Carbon Materials 2014, 29(2): 81–88]

Doping mechanisms in graphene-MoS2 hybrids

We present a joint theoretical and experimental investigation of charge doping and electronic potential landscapes in hybrid structures composed of graphene and semiconducting single layer molybdenum disulfide (MoS2). From first-principles simulations, we find electron doping of graphene due to the presence of rhenium impurities in MoS2. Furthermore, we show that MoS2 edges give rise to charge reordering and a potential shift in graphene, which can be controlled through external gate voltages. The interplay of edge and impurity effects allows the use of the graphene-MoS2 hybrid as a photodetector. Spatially resolved photocurrent signals can be used to resolve potential gradients and local doping levels in the sample.

Graphene–MoS2 hybrid structures for multifunctional photoresponsive memory devices

Combining the electronic properties of graphene and molybdenum disulphide (MoS2) in hybrid heterostructures offers the possibility to create devices with various functionalities. Electronic logic and memory devices have already been constructed from graphene-MoS2 hybrids, but they do not make use of the photosensitivity of MoS2, which arises from its optical-range bandgap. Here, we demonstrate that graphene-on-MoS2 binary heterostructures display remarkable dual optoelectronic functionality, including highly sensitive photodetection and gate-tunable persistent photoconductivity. The responsivity of the hybrids was found to be nearly 1×10(10) AW(-1) at 130K and 5×10(8)AW(-1) at room temperature, making them the most sensitive graphene-based photodetectors. When subjected to time-dependent photoillumination, the hybrids could also function as a rewritable optoelectronic switch or memory, where the persistent state shows almost no relaxation or decay within experimental timescales, indicating near-perfect charge retention. These effects can be quantitatively explained by gate-tunable charge exchange between the graphene and MoS2 layers, and may lead to new graphene-based optoelectronic devices that are naturally scalable for large-area applications at room temperature.

Flexible and robust MoS2–graphene hybrid paper cross-linked by a polymer ligand: a high-performance anode material for thin film lithium-ion batteries

A flexible and robust MoS2-graphene hybrid paper with an excellent lithium storage capacity is fabricated through cross-linking by a polymer ligand, PEO, and shows potential for the development of high-performance film anodes.